Method for hydrogenating carbonyl compounds

ABSTRACT

In a process for the catalytic hydrogenation of a carbonyl compound or a mixture of two or more carbonyl compounds in the presence of catalyst tablets which comprise an inorganic, TiO 2 -containing support and, as active component, copper or a mixture of copper with at least one metal selected from the group consisting of zinc, aluminum, cerium, nobel metals and metals of transition group VIII and whose copper surface area is not more than 10 m 2 /g, the diameter d and/or the height h of the tablets is less than 3 mm.

[0001] The invention relates to a process for the catalytichydrogenation of carbonyl compounds in the presence of copper-containingcatalyst tablets and to the copper-containing catalyst tabletsthemselves.

[0002] The catalytic hydrogenation of carbonyl compounds such asaldehydes for producing simple and functionalized alcohols is acquiringan important position in production streams of the basic chemicalsindustry. This applies particularly to the hydrogenation of aldehydeswhich are obtainable via the oxo process or the aldol reaction.

[0003] The catalytic hydrogenation of carbonyl compounds is carried outvirtually exclusively in fixed-bed reactors in industrial processes.Catalysts used include not only catalysts of the Raney type but also, inparticular, supported catalysts, for example copper, nickel or nobelmetal catalysts.

[0004] U.S. Pat. No. 3,923,694 describes, for example, a catalyst of thecopper oxide/zinc oxide/aluminum oxide type. The disadvantage of thiscatalyst is that it is not sufficiently mechanically stable during thereaction and therefore disintegrates relatively quickly. This results ina loss in activity and a buildup of a differential pressure over thereactor due to the disintegrating catalyst bodies. As a consequence, theplant has to be shut down prematurely.

[0005] DE-A 195 05 347 describes in quite general terms a process forproducing catalyst tablets having a high mechanical strength, in which ametal powder or a powder of a metal alloy is added to the material to betabletted. For example, aluminum powder or copper powder is added asmetal powder. However, the addition of aluminum powder in the case of acopper oxide/zinc oxide/aluminum oxide catalyst results in a shaped bodywhich has a worse lateral compressive strength than a shaped body whichhas been produced without addition of aluminum powder, and the shapedbody of the invention when used as catalyst displayed a worse conversionactivity than catalysts which had been produced without addition ofaluminum powder. The document likewise discloses a hydrogenationcatalyst comprising NiO, ZrO₂, MoO₃ and CuO to which Cu powder, interalia, was added during production. However, this document says nothingabout the selectivity or the activity.

[0006] DE 198 09 418 describes a process for the catalytic hydrogenationof a carbonyl compound in the presence of a catalyst comprising asupport consisting predominantly of titanium dioxide and, as activecomponent, copper or a mixture of copper with at least one metalselected from the group consisting of zinc, aluminum, cerium, nobelmetals and metals of transition group VIII, where the copper surfacearea is not more than 10 m²/g. Preferred support materials are mixturesof titanium dioxide with aluminum oxide or zirconium oxide or aluminumoxide and zirconium oxide. In a preferred embodiment, the catalystmaterial is shaped with addition of metallic copper powder.

[0007] It is an object of the present invention to provide a process forthe catalytic hydrogenation of carbonyl compounds using a catalyst whichcan be produced industrially in a simple manner, has a sufficiently highmechanical stability under the reaction conditions occurring in such aprocess and, in particular makes it possible to achieve long catalystoperating lives and high conversions and selectivities.

[0008] It has been found that tabletting a dried powder comprising thesupport material, the active component and a customary tabletting aid,e.g. graphite, together with metallic Cu powder to form catalyst tabletshaving a diameter d and/or a height h of less than 3 mm leads to highactivities and selectivities and to good stability of the catalyst.

[0009] Accordingly, the abovementioned object is achieved by a processfor the catalytic hydrogenation of a carbonyl compound or a mixture oftwo or more carbonyl compounds in the presence of catalyst tablets whichcomprise an inorganic, TiO₂-containing support and, as active component,copper or a mixture of copper with at least one metal selected from thegroup consisting of zinc, aluminum, cerium, nobel metals and metals oftransition group VIII and whose copper surface area is not more than 10m²/g, wherein the diameter d and/or the height h of the tablets is lessthan 3 mm.

[0010] As support, preference is given to using TiO₂ or a mixture ofTiO₂ and Al₂O₃ or a mixture of TiO₂ and ZrO₂ or a mixture of TiO₂, Al₂O₃and ZrO₂, particularly preferably TiO₂.

[0011] The catalyst used in the process of the present invention isproduced by applying the active component copper to the support materialused, with there being no restrictions in respect of the applicationmethod.

[0012] In particular, the following application methods are possible:

[0013] a) application of a copper salt solution in one or moreimpregnation steps to a previously produced inorganic support. Thesupport is dried after the impregnation and calcined if appropriate.

[0014] a1) The impregnation can be carried out by the “incipientwetness” method in which the support is treated with an amount of theimpregnation solution corresponding to its water absorption capacity sothat it is just saturated. However, the impregnation can also be carriedout with the support covered by the solution.

[0015] a2) In multistage impregnation processes it is advantageous todry and if appropriate calcine the support between individualimpregnation steps. Multistage impregnation is particularly advantageouswhen the support is to be treated with a relatively large amount ofcopper.

[0016] a3) The inorganic support material is preferably used as apreshaped composition in the impregnation, for example as powder,spheres, extrudates or tablets. Particular preference is given to usingpowder.

[0017] a4) As solvent for the copper salts, preference is given to usingconcentrated aqueous ammonia.

[0018] b) Precipitation of a copper salt solution onto a previouslyproduced, inert inorganic support. In a particularly preferredembodiment, the latter is present as a powder in an aqueous suspension.

[0019] b1) In one embodiment (i), a copper salt solution isprecipitated, preferably by means of sodium carbonate solution. Asinitial charge, use is made of an aqueous suspension of the supportmaterial.

[0020] b2) In a further embodiment (ii), the precipitated catalyst canbe produced in a two-stage process. Here, the first step comprisesproducing and drying a powder as described in a). This powder isconverted into an aqueous suspension and used as substrate in a secondstep equivalent to embodiment (i).

[0021] The precipitated solids resulting from a) or b) are filtered offin a customary manner and preferably washed free of alkali.

[0022] Both the final products from a) and those from b) are dried atfrom 50 to 150° C., preferably at 120° C., and subsequently calcined ifappropriate, preferably for 2 hours at generally from 200 to 400° C., inparticular from 200 to 220° C.

[0023] As starting materials for a) and/or b), it is in principlepossible to use all Cu(I) and/or Cu(II) salts soluble in the solventsused for the application to the support, for example sulfates, nitrates,chlorides, carbontes, acetates, oxalates or ammonium complexes. Formethod a), particular preference is given to using copper carbonate,while method b) is particularly preferably carried out using coppernitrate.

[0024] To produce the catalyst tablets of the present invention, theabove-described dried powder is shaped by means of a suitable tablettingpress to form tablets having a diameter d of less than 3 mm and/or aheight h of less than 3 mm, preferably d and/or h of less than 2 mm,particularly preferably d and/or h of 1.5 mm. As tabletting aid,graphite is added in the shaping process, preferably in an amount of 3%by weight, based on the weight of the dried powder.

[0025] As further additive in addition to the above-described powder andto graphite, metallic Cu powder is added in the production of thecatalyst. Preference is given to adding, based on the weight of theabove-described dried powder, from 5 to 40% by weight of metallic Cupowder, in particular from 15 to 20% by weight.

[0026] The catalyst tablets can be symmetrical, i.e. the height h andthe diameter d are identical, or unsymmetrical, i.e. the height h anddiameter d are different, but d and/or h are less than 3 mm. In the caseof the unsymmetrical tablets, the ratio d:h can be up to 1:2, i.e. themaximum height of the tablets is twice the diameter of the tablets. Inthe process of the present invention, particular preference is given tousing symmetrical catalyst tablets in which the diameter d and theheight h are each 1.5 mm.

[0027] The present invention therefore also provides a catalyst tabletwhich comprises an inorganic support comprising TiO₂ and, as activecomponent, copper or a mixture of copper with at least one metalselected from the group consisting of zinc, aluminum, cerium, nobelmetals and metals of transition group VIII, whose copper surface area is10 m²/g and which is obtainable by a process which comprises atabletting step in which metallic copper powder is added, wherein thediameter d and/or the height h of the tablet is less than 3 mm.

[0028] The shaped tablets of the present invention are preferablyheat-treated for 2 hours at from 300 to 600° C., in particular from 400to 500° C. This novel tabletting process allows, compared to theexclusive use of graphite as tabletting aid in the customary processes,the powder to be shaped to form tablets particularly easily and givesvery chemically and mechanically stable catalysts.

[0029] The surface area of the catalyst tablet is determined by the BETmethod using N₂ adsorption, in particular as specified in DIN 66 131.The mean pore diameter and the pore size distribution are determined bymeans of Hg porosimetry, in particular as specified in DIN 66 133.

[0030] The parameters “hardness” and “abrasion” can be determined asfollows. To determine the cutting hardness, specimens are parted bymeans of a blade. The force which has to be applied to the blade to cutthrough the specimen is referred to as the cutting hardness of thematerial.

[0031] The fracture hardness (fracture strength) of spherical specimensis determined by placing the sphere under a punch having a defined areaand pressing the punch against the sphere until the latter breaks. Thepressure which needs to be applied to the specimen by the punch forfracture to occur is referred to as the fracture hardness.

[0032] The abrasion is determined by means of a vibratory mill. In thistest, catalyst material having a particular particle size range isaggitated together with porcelain balls in a container at a highrotation rate for a particular period of time. The catalyst is thensieved out again. The weight loss in percent is then designated as theabrasion, as is described in chapter 6 of J.-F. Le Page et al., “AppliedHeterogeneous Catalysis”, Editions Technip, Paris (1987).

[0033] The lateral compressive strength is determined for the purposesof the present invention by means of an instrument model “Z 2.5/T 919”from Zwick (Ulm), and the abrasion was determined in accordance withASTM Designation D 4058-81. The measurements were carried out under anitrogen atmosphere to avoid reoxidation of the catalysts.

[0034] Activation of the ignited catalyst is carried out either beforeor after installation in the reactor.

[0035] If the catalyst is to be used in its reduced form, it isinstalled in the reactor and supplied directly with the hydrogenationsolution under hydrogen pressure. When it is used in the oxidic form,the catalyst is prereduced by means of reducing gases, for examplehydrogen, preferably hydrogen/inert gas mixtures, in particularhydrogen/nitrogen mixtures, at from 100 to 300° C., preferably from 150to 250° C., in particular from 180 to 240° C., before it is suppliedwith the hydrogenation solution. Preference is given to using a mixturehaving a hydrogen content of from 1 to 100% by volume for theprereduction.

[0036] A characteristic parameter of the catalysts of the presentinvention is the specific copper surface area. This is calculated fromthe N₂O consumption determined in the oxidation of surface copper atomsby gaseous N₂O in a heated sample.

[0037] For this purpose, the sample is firstly treated with 10 mbar ofhydrogen at 240° C. for 10 minutes. The sample is subsequently evacuatedto a pressure of less than 10-3 mbar and is then treated with 30 mbar ofH₂ for 10 minutes, subsequently evacuated once more to less than 10-3mbar, treated with 100 mbar of H₂ for 3 hours, evacuated again to lessthan 10-3 mbar and finally treated with 200 mbar of H₂ for 15 hours,with the treatment with hydrogen being carried out in each case at 240°C.

[0038] In a second step, the sample is treated with N₂O at 70° C. and apressure of 266 mbar for 2 hours, during which decomposition of the N₂Oon the sample can be observed. The sample is subsequently evacuated toless than 10-3 mbar and the increase in the mass of the catalyst as aresult of formation of copper oxide on the surface of the catalyst isthen determined.

[0039] The specific copper surface area measured in this way on thecatalysts produced according to the present invention is generally notmore than 10 m²/g, preferably from 0.1 to 10 m²/g, more preferably inthe range from 0.5 to 7 m²/g, in particular in the range from 0.5 to 5m²/g.

[0040] The present invention therefore also provides a catalyst tabletwhich comprises an inorganic, TiO₂-containing support and, as activecomponent, copper or a mixture of copper with at least one metalselected from the group consisting of zinc, aluminum, cerium, nobelmetals and metals of transition group VIII and whose copper surface areais not more than 10 m²/g, wherein the diameter d and/or the height h ofthe tablet is less than 3 mm.

[0041] A preferred field of application for the catalyst tabletsproduced according to the present invention is hydrogenation in a fixedbed. However, use in a fixed-bed reaction with upward and downwardswirling motion of the catalyst material is likewise possible. Thehydrogenation can be carried out in the gas phase or in the liquidphase. The hydrogenation is preferably carried out in the liquid phase,for example in the downflow or upflow mode.

[0042] In the downflow mode, the liquid feed comprising the carbonylcompound to be hydrogenated is allowed to trickle over the catalyst bedin the reactor which is under hydrogen pressure, so that a thin liquidfilm is formed on the catalyst. In contrast, when the upflow mode isemployed, hydrogen gas is introduced into the reactor which is floodedwith the liquid reaction mixture, so that the hydrogen ascends as gasbubbles through the catalyst bed.

[0043] In one embodiment, the solution to be hydrogenated is pumped in asingle pass through the catalyst bed. In another embodiment of theprocess of the present invention, part of the product which has passedthrough the reactor is continuously taken off as product stream andoptionally passed through a second reactor as defined above. The otherpart of the product is fed back into the reactor together with freshfeed comprising the carbonyl compound. This mode of operation willhereinafter be referred to as the circulation mode.

[0044] If the downflow mode is chosen as embodiment of the process ofthe present invention, preference is given to the circulation mode. Morepreferably, the process is carried out in the circulation mode using amain reactor and an after-reactor.

[0045] The process of the present invention is suitable forhydrogenating carbonyl compounds such as aldehydes and ketones to formthe corresponding alcohols, with preference being given to aliphatic andcycloaliphatic saturated and unsaturated carbonyl compounds. In the caseof aromatic carbonyl compounds, formation of undesirable by-products canoccur as a result of hydrogenation of the aromatic ring. The carbonylcompounds may bear further functional groups such as hydroxy or aminogroups. Unsaturated carbonyl compounds are generally hydrogenated to thecorresponding saturated alcohols. The term “carbonyl compounds” as usedfor the purposes of the invention encompasses all compounds whichcontain a C═O group, including carboxylic acids and their derivatives.It is of course also possible to hydrogenate two or more carbonylcompounds together. Furthermore, the individual carbonyl compound to behydrogenated may contain more than one carbonyl group.

[0046] The process of the present invention is preferably employed forthe hydrogenation of aliphatic aldehydes, hydroxy aldehydes, ketones,acids, esters, anhydrides, lactones and sugars.

[0047] Preferred aliphatic aldehydes are branched and unbranchedsaturated and/or unsaturated aliphatic C₂-C₃₀-aldehydes, as areobtainable, for example, from linear or branched olefins having aninternal or terminal double bond by means of the oxo process. Oligomericcompounds which may contain more than 30 carbonyl groups can also behydrogenated.

[0048] Examples of aliphatic aldehydes are:

[0049] formaldehyde, propionaldehyde, n-butyraldehyde, isobutyraldehyde,valeraldehyde, 2-methylbutyraldehyde, 3-methylbutyraldehyde(isovaleraldehyde), 2,2-dimethylpropionaldehyde (pivalinaldehyde),caproaldehyde, 2-methylvaleraldehyde, 3-methylvaleraldehyde,4-methylvaleraldehyde, 2-ethylbutyraldehyde, 2,2-dimethylbutyraldehyde,3,3-dimethylbutyraldehyde, caprylic aldehyde, capric aldehyde,glutaraldehyde.

[0050] Apart from the short-chain aldehydes mentioned, it is alsopossible to use, in particular, long-chain aliphatic aldehydes as can beobtained, for example, from linear α-olefins by means of the oxoprocess.

[0051] Particular preference is given to enalization products such as2-ethylhexenal, 2-methylpentenal, 2,4-diethyloctenal or2,4-dimethylheptenal.

[0052] Preferred hydroxyaldehydes are C₃-C₁₂-hydroxyaldehydes as areobtainable, for example, from aliphatic and cycloaliphatic aldehydes andketones by aldol reaction with themselves or formaldehyde. Examples are3-hydroxypropanal, dimethylolethanal, trimethylolethanal(pentaerythrital), 3-hydroxybutanal (acetaldol),3-hydroxy-2-ethylhexanal (butyl aldol), 3-hydroxy-2-methylpentanal(propyl aldol), 2-methylolpropanal, 2,2-dimethylolpropanal,3-hydroxy-2-methylbutanal, 3-hydroxypentanal, 2-methylolbutanal,2,2-dimethylolbutanal, hydroxypivalaldehyde. Particular preference isgiven to hydroxypivalaldehyde (HPA) and dimethylolbutanal (DMB).

[0053] Preferred ketones are acetone, butanone, 2-pentanone,3-pentanone, 2-hexanone, 3-hexanone, cyclohexanone, isophorone, methylisobutyl ketone, mesityl oxide, acetophenone, propiophenone,benzophenone, benzalacetone, dibenzalacetone, benzalacetophenone,2,3-butanedione, 2,4-pentanedione, 2,5-hexanedione and methyl vinylketone.

[0054] Furthermore, carboxylic acids and derivatives thereof, preferablyones having 1-20 carbon atoms, can also be reacted. Particular mentionmay be made of the following:

[0055] carboxylic acids such as formic acid, acetic acid, propionicacid, butyric acid, isobutyric acid, n-valeric acid, trimethylaceticacid (“pivalic acid”), caproic acid, enanthic acid, caprylic acid,capric acid, lauric acid, myristic acid, palmitic acid, stearic acid,acrylic acid, methacrylic acid, oleic acid, elaidic acid, linoleic acid,linolenic acid, cyclohexanecarboxylic acid, benzoic acid, phenylaceticacid, o-toluic acid, m-toluic acid, p-toluic acid, o-chlorobenzoic acid,p-chlorobenzoic acid, o-nitrobenzoic acid, p-nitrobenzoic acid,salicylic acid, p-hydroxybenzoic acid, anthranilic acid, p-aminobenzoicacid, oxalic acid, malonic acid, succinic acid, glutaric acid, adipicacid, pimelic acid, suberic acid, azelaic acid, sebacic acid, maleicacid, fumaric acid, phthalic acid, isophthalic acid, terephthalic acid;

[0056] carboxylic acid halides such as the chlorides or bromides of theabovementioned carboxylic acids, in particular acetyl chloride orbromide, stearoyl chloride or bromide and benzoyl chloride or bromide,which are, in particular, dehalogenated;

[0057] carboxylic esters such as the C₁-C₁₀-alkyl esters of theabovementioned carboxylic acids, in particular methyl formate, ethylacetate, butyl butyrate, dimethyl terephthalate, dimethyl adipate,dimethyl maleate, methyl (meth)acrylate, butyrolactone, caprolactone andpolycarboxylic esters such as polyacrylic and polymethacrylic esters andtheir copolymers and polyesters such as polymethyl methacrylate,terephthalic esters and other industrial polymers; in these cases, inparticular, hydrogenolyses, i.e. the conversion of esters into thecorresponding acids and alcohols, are carried out;

[0058] fats;

[0059] carboxylic anhydrides such as the anhydrides of theabovementioned carboxylic acids, in particular acetic anhydride,propionic anhydride, benzoic anhydride and maleic anhydride;

[0060] carboxylic amides such as formamide, acetamide, propionamide,stearamide and terephthalamide.

[0061] Furthermore, hydroxycarboxylic acids, e.g. lactic, malic,tartaric or citric acid, or amino acids, e.g. glycine, alanine, prolineand arginine, and peptides can also be reacted.

[0062] The process of the present invention is particularly preferablyused for hydrogenating aldehydes and hydroxyaldehydes.

[0063] The carbonyl compound to be hydrogenated can be fed to thehydrogenation reactor either alone or as a mixture with the product ofthe hydrogenation reaction. The carbonyl compound can be used inundiluted form or an additional solvent can be employed. Suitableadditional solvents are, in particular, water and alcohols such asmethanol, ethanol and the alcohol which is formed under the reactionconditions. Preferred solvents are water, THF, NMP and ethers such asdimethyl ether, diethyl ether and MTBE; particular preference is givento water.

[0064] The hydrogenation both in the upflow mode and in the downflowmode, in each case preferably using the circulation mode, is generallycarried out at from 50 to 250° C., preferably from 70 to 200° C.,particularly preferably from 100 to 140° C., and a pressure of from 15to 250 bar, preferably from 20 to 200 bar, particularly preferably from25 to 100 bar.

[0065] High conversions and selectivities are achieved in the process ofthe present invention and the catalysts display a high chemicalstability in the presence of the reaction mixture. For the same supportmaterial, the catalysts produced according to the present invention are,compared to catalysts which have been produced according to the priorart, both easier to shape into tablets and, after heat treatment of theshaped tablets, have a significantly greater mechanical strength both inthe oxidic state and in the reduced state, as a result of which theprocess of the present invention is particularly economical.

[0066] The invention is illustrated by the following examples.

EXAMPLES

[0067] Catalyst Production

[0068] All percentages reported under this subheading are by weightunless indicated otherwise. The stated percentage compositions are basedon the oxidic constituents of the finished catalysts.

[0069] Catalyst A (Comparison)

[0070] Catalyst A was produced by precipitation of a solution of coppernitrate with sodium carbonate solution. As substrate, use was made of asuspension of TiO₂ in water. The precipitated material formed in theprecipitation was filtered off, washed and dried at 120° C. The driedpowder was calcined at 200° C. for two hours and then mixed with 3% byweight of graphite and 20% by weight of metallic copper powder andpressed to form tablets having a diameter of 3 mm and a height of 3 mm.These tablets were calcined at 450° C. for 2 hours. The finishedcatalyst comprised 60% of CuO and 40% of TiO₂ and had a tapped densityof 1498 g/l, a pore volume determined by Hg porosimetry of 0.21 ml/g, aBET surface area of 23.6 m²/g, a copper surface area of 1.7 m²/g and alateral compressive strength of 54.5 N.

[0071] Catalyst B

[0072] The catalyst B according to the present invention was produced inthe same way as catalyst A, except that it was pressed to form tabletshaving a diameter of 1.5 mm and a height of 1.5 mm. The finishedcatalyst comprised 60% of CuO and 40% of TiO₂ and had a tapped densityof 1529 g/l, a pore volume determined by Hg porosimetry of 0.21 ml/g, aBET surface area of 26.8 m²/g, a copper surface area of 1.8 m²/g and alateral compressive strength of 32.1 N.

Example 1

[0073] Hydrogenation of Dimethylolbutanal (DMB) to Trimethylolpropane(TMP) in the Downflow Mode with Recirculation and an After-Reactor

[0074] The starting solution employed was a mixture of 30% of DMB and70% of water. This mixture was hydrogenated by means of the catalysts Aand B in a reactor having a volume of 210 ml (130 ml main reactor and 80ml after-reactor) in the circulation mode at a throughput of 7.5 l/h andtemperatures of 120° C. (main reactor) and 130° C. (after-reactor) and apressure of 90 bar, with the WHSV over the catalyst being from 0.2kg_(DMB)/(1_(cat)·h) and 2 kg_(DMB)/(1_(cat)·h).

[0075] Table 1 shows a comparison of the catalyst B according to thepresent invention with the catalyst A which is not according to thepresent invention and illustrates the high conversions and selectivitiesof B. TABLE 1 Results from example 1 (downflow mode with recirculationand after-reactor) WHSV [ kg/l*h ] Catalyst A Catalyst B Conversion/%0.2 99.6 99.9 (from GC % by 0.7 97.9 99.7 area) 1.2 96.4 99.1 2.0 89.292.8 Selectivity/% 0.2 92.6 93.8 (from GC % by 0.7 92.4 93.7 area) 1.291.1 93.4 2.0 88.5 90.2

We claim:
 1. A process for the catalytic hydrogenation of an aliphatichydroxyaldehyde or a mixture of two or more of these aldehydes in thepresence of catalyst tablets which comprise an inorganic,TiO₂-containing support and, as active component, copper or a mixture ofcopper with at least one metal selected from the group consisting ofzinc, aluminum, cerium, nobel metals and metals of transition group VIIIand whose copper surface area is not more than 10 m²/g, metallic copperpowder being added to the catalyst material prior to tabletting, whereinthe diameter d and/or the height h of the tablets is in each case 1.5mm.
 2. A process as claimed in claim 1, wherein the support materialcomprises a mixture of TiO₂ and Al₂O₃ or a mixture of TiO₂ and ZrO₂ or amixture of TiO₂ and Al₂O₃ and ZrO₂.
 3. A process as claimed in any ofclaims 1 to 2, wherein the diameter and height of the catalyst tabletsare equal.
 4. A catalyst tablet which comprises an inorganic,TiO₂-containing support and, as active component, copper or a mixture ofcopper with at least one metal selected from the group consisting ofzinc, aluminum, cerium, nobel metals and metals of transition group VIIIand whose copper surface area is not more than 10 m²/g, metallic copperpowder being added to the catalyst material prior to tabletting, whereinthe diameter d and/or the height h of the tablet is in each case 1.5 mm.5. A catalyst tablet as claimed in claim 4, wherein the diameter andheight of the tablet are equal.